The present invention relates to a lawn mower blade sharpening apparatus and especially to a blade sharpening apparatus for use with a standard bench grinder mounted on a workbench.
Lawn mower blades for rotary lawn mowers require frequent sharpening as a result of the blade becoming dull from the operation of the lawn mower cutting grass, weeds and the like and from the blade surface becoming roughened by impact with sand, gravel and small objects in the path of the lawn mower blade. Rotary lawn mower blades typically are one elongated flat member having opposite surfaces thereon sharpened at a predetermined angle. The blades are attached to a rotating shaft enclosed in a housing and rotate the sharpened edges to cut grass.
There have been a variety of lawn mower blade sharpening devices provided in the past, some of which sharpen the blade while still attached to the lawn mower while others remove the blade for sharpening. One prior art U.S. Pat. No. 5,062,322 to Sinko is a self-contained electric motor driven lawn mower blade sharpening machine for use in sharpening rotary lawn mower blades. The machine has a base for mounting the motor drive with an abrasive wheel and a free floating blade guide which allows sharpening of unevenly worn blades to a beveled angle of 30 degrees along the contoured cutting edge. In the Shanelec U.S. Pat. No. 4,936,053 a lawn mower blade sharpener apparatus is attachable to an existing bench grinder assembly having a rotating grinding wheel to sharpen an edge portion on a lawn mower blade and includes a stationary grinder attachment assembly which is clamped to an object support assembly on the bench grinder assembly. A pair of movable blade attachment assemblies holding and move a blade across the grinder. The Horrell U.S. Pat. No. 4,265,146 is a device for sharpening a lawn mower blade having an abrasive wheel attached thereto. A base holds the drill in a substantially horizontal position and a clamp holds the lawn mower blade and has a rail adjustably attached to the base. A rail follower is slidably attached to the rail for reciprocating movement thereon substantially parallel to the longitudinal axis of the abrasive wheel to sharpen a blade clamped to the rail follower. The Thomas U.S. Pat. No. 4,841,678 is a tool sharpening apparatus for use in combination with a grinding wheel aligned for multiple adjustment and angular displaceable supports for sharpening tools.
The present invention is directed for sharpening a lawn mower blade at different angles and which utilizes an existing bench grinder attached to a work bench. A frame with a blade supporting surface is attached to the workbench over the bench grinder grinding wheel. The use of an existing bench grinder with a simplified blade support reduces the cost and simplifies the operation of the lawn mower blade sharpener of the present invention.